SUPPLEMENTARY INFORMATION:

I. General Information

Written Comments

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2014-0128, at https://www.regulations.gov (our preferred method), or the other methods identified in the ADDRESSES section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov any information you consider to be Confidential Business Information (CBI), Proprietary Business Information (PBI), or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( i.e., on the web, cloud, or other file sharing system). Please visit https://www.epa.gov/​dockets/​commenting-epa-dockets for additional submission methods; the full EPA public comment policy; information about CBI, PBI, or multimedia submissions; and general guidance on making effective comments.

II. Information About the Documents

Two sections of the Clean Air Act (CAA or the Act) govern the establishment and revision of the NAAQS. Section 108 directs the Administrator to identify and list certain air pollutants and then issue “air quality criteria” for those pollutants. The air quality criteria are to “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of such pollutant in the ambient air. . .” (CAA section 108(a)(2)). Under section 109 of the Act, the EPA is then to establish primary (health-based) and secondary (welfare-based) NAAQS for each pollutant for which the EPA has issued air quality criteria. Section 109(d)(1) of the Act requires periodic review and, if appropriate, revision of existing air quality criteria. Revised air quality criteria are to reflect advances in scientific knowledge on the effects of the pollutant on public health and welfare. Under the same provision, the EPA is also to periodically review and, if appropriate, revise the NAAQS, based on the revised air quality criteria. The Act additionally requires appointment of an independent scientific review committee that is to periodically review the existing air quality criteria and NAAQS and to recommend any new standards and revisions of existing criteria and standards as may be appropriate (CAA section 109(d)(2)(A)-(B)). Since the early 1980s, the requirement for an independent scientific review committee has been fulfilled by the Clean Air Scientific Advisory Committee (CASAC).

In characterizing effects related to atmospheric deposition of oxides of nitrogen and oxides of sulfur and their transformation products, this review also recognizes the contribution of PM through deposition to eutrophication-related effects, acidification-related effects, and other such welfare effects, as well to the direct and other indirect effects on vegetation, soils, and biota. Addressing the pollutants together enables us to take a comprehensive look at the nature and interactions of the pollutants, which is important for ensuring that all scientific information relevant to ecological effects is thoroughly evaluated. This approach also addresses the CASAC's comments on the draft Integrated Review Plan (IRP) for this review, as well as the CASAC's comments on the draft IRP for the PM NAAQS review. In particular, the CASAC expressed concern that PM deposition-related effects were not adequately covered in the PM review; and they also encouraged the EPA to include all reduced nitrogen compounds, including ammonia and ammonium, to properly evaluate ecological impacts from nitrogen deposition in the secondary standards review for oxides of nitrogen and oxides of sulfur (Diez Roux and Fernandez, 2016; Diez Roux, 2016). Additional welfare effects associated with PM, such as visibility impairment, climate effects and materials damage, and the health effects of PM (including particulate transformation products of oxides of nitrogen and oxides of sulfur) are considered as part of the separate review of the NAAQS for PM.

In March 2017, EPA released the first external review draft of the Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides of Sulfur, and Particulate Matter Ecological Criteria, which was then discussed at a CASAC meeting May 24-25, 2017. Comments from the CASAC (Diez Roux, 2017) and the public were considered in preparing the second external review draft (June 2018), which was then discussed at a CASAC meeting September 5-6, 2018, and April 27, 2020. CASAC provided a final letter on the second draft ISA in May 2020 (Cox, 2020), and in October 2020, EPA released the final ISA for NO_X, SO_X, and PM ecological criteria (U.S. EPA, 2020).

This draft PA serves to “bridge the gap” between the scientific and technical information in the 2020 ISA and any air quality, exposure, and risk analyses available in this review, and the judgments required of the Administrator in determining whether to retain or revise the existing secondary ambient air quality standards for NO₂, SO₂ and PM. The draft PA document will be available on or about May 31, 2023, on EPA's website at https://www.epa.gov/​naaqs/​nitrogen-dioxide-no2-and-sulfur-dioxide-so2-secondary-air-quality-standards. The EPA is soliciting advice and recommendations from the CASAC by means of a review of this draft document in an upcoming public meeting of the CASAC. Information about this public meeting, including the dates and location, was published as a separate notice in the Federal Register on March 23, 2023 (88 FR 17572). Following the CASAC meeting, the EPA will consider comments received from the CASAC and the public in preparing the final PA.

The Draft PA will be available primarily via the internet at: https://www.epa.gov/​naaqs/​nitrogen-dioxide-no2-and-sulfur-dioxide-so2-secondary-air-quality-standards. The document will be accessible under “Policy Assessments” from the current review. The draft document briefly described above does not represent and should not be construed to represent any final EPA policy, viewpoint, or determination.

88 FR 34852